Creating and manipulating graphs

Creating a new graph

To create a new Tulip graph from Python, the tlp.newGraph() function has to be used. It returns an empty graph which is an instance of the tlp.Graph class.

graph = tlp.newGraph()

Importing / exporting a graph using the TLP file format

TLP is the Tulip format to save a graph and its associated data to a file. The extension of the file can be .tlp or .tlp.gz (compressed version).

Loading a graph from a TLP file

To load a graph saved in TLP into a Python oject, the tlp.loadGraph() function has to be used. It loads the graph described in the file and its associated data and returns an instance of the tlp.Graph. For instance, the sample code below imports the graph saved to the file /home/foo/savedgraph.tlp:

graph = tlp.loadGraph("/home/foo/savedgraph.tlp")

Saving a graph to a TLP file

To save an instance of a tlp.Graph class to a TLP file, the tlp.saveGraph() function has to be used. It saves the graph and its associated data into a file. For instance, the sample code below exports a graph to the file /home/foo/mygraph.tlp:

tlp.saveGraph(graph, "/home/foo/mygraph.tlp")

Adding / Removing elements in the graph

The graph structure can be freely modified through dedicated methods of the tlp.Graph class (see Modification of the graph structure) . Below is a list of some of these methods :

• Adding elements to the graph : tlp.Graph.addNode(), tlp.Graph.addEdge()
• Removing elements from the graph : tlp.Graph.delNode(), tlp.Graph.delEdge(), tlp.Graph.clear()

Iterating over graph elements

The tlp.Graph class provides several iterators on the graph structure (see Iterators on the graph structure). The sample code below illustrates the syntax to perform an iteration over all the nodes of a graph.:

for n in graph.getNodes():
  degree = graph.deg(n)
  print "the degree of ", n, "is ", degree